Insects such as mosquitoes use their olfactory and gustatory systems to find their hosts and in the process can transmit deadly diseases to hundreds of millions of people worldwide causing substantial mortality and morbidity. The chemosensory receptors therefore provide excellent targets to design behavior disruption strategies. The insect repellent DEET is effective against a variety of insects including mosquitoes; however it is rarely used by the population at risk in tropical countries due to high costs relative to incomes, and the inconvenience of continuous application on skin. The effectiveness of DEET is due in part to it being detected by aversive receptors in both the olfactory and the gustatory system; however nothing was known about their identity. In a recent breakthrough using the model system Drosophila melanogaster we have identified a DEET-detecting neuron in the antenna that expresses Ir40a and we have shown that both the neuron and the gene are required for avoidance. We have also developed a cheminformatic method to predict new ligands for the DEET receptor that are from natural sources including compounds found in food and flavoring. The goal of this proposal is to identify the conserved DEET-sensing olfactory and gustatory receptors and utilize them as targets to create novel classes of powerful broad-spectrum insect repellents that are safe and affordable. In addition high-throughput assay platforms with the target receptors for DEET will be created, which will serve as a foundation for discovery of even better repellents in the future. For this proposal we plan to use an array of technologies that involve chemical-informatics, neurophysiology, and behavioral analysis. First, we plan to validate the role of the Ir40a/Ir93a/Ir25a in detection of DEET and use them to test the computationally predicted ligands. Second, we plan to identify gustatory receptors that detect DEET as bitter and then test the predicted ligands as bitter aversive compounds. Third, we propose to identify neuronal circuits in the higher brain centers that process the aversive behavior from the olfactory and gustatory system. And fourth, we will test the dual aversive compounds for repellency in Aedes aegypti mosquitoes transmits Dengue and Yellow fever. Successful completion of this proposal will provide safe, affordable and pleasant smelling odorants that are better than DEET in reducing contact between humans and mosquitoes.